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A dense Cu-10Sn alloy bulk specimen was obtained by optimizing the laser powder bed fusion (L-PBF) processing, and the relative density of the specimen reached 99.7%. The grain morphology was mainly the columnar dendrite and inter-dendritic phases generated along the solidification direction. Tensile testing and detailed microstructural characterization were carried out on specimens in the as-built and heat-treated condition. Under the quasi-static tensile condition, the yield strength (σ0.2), ultimate tensile strength (UTS), and the elongation of the as-built Cu-10Sn specimen were 392 MPa, 749 MPa and 29%, respectively. After the solution treatment at 800 °C for 4 h, and aging treatment at 400 °C for 2 hours, the microstructure of the specimen transformed from the columnar grain to equiaxed grain, the dislocation density decrease, and numerous annealing twins were observed in the heat-treated state. Therefore, the quasi-static tensile yield strength (σ0.2) of the specimen was reduced to 245 MPa. However, the UTS and the elongation were increased to 840 MPa and 56%, respectively, due to the interaction between annealing twins and equiaxed grain. [ABSTRACT FROM AUTHOR]

The effects of chromium content on microstructure, hardness and wear resistance of as-cast Fe-xCr-1.0B (x = 0, 4, 8, 12, 16, 20) alloys were investigated by means of optical microscope (OM), scanning electron microscope (SEM), x-ray diffractometer (XRD), hardness tester and ring block wear tester. The results showed that the microstructures of chromium-free alloy were mainly composed of pearlite, ferrite, and eutectic borocarbides, and the hardness was very low, only 18.8 HRC. With the increase in chromium content, the matrix of as-cast Fe-Cr-B alloy gradually began to transform from pearlite and ferrite to lath martensite, and the type of borocarbides changed from Fe2(B, C) to M2(B, C), M7(C, B)3 and M23(C, B)6 (M = Fe, Cr). When the chromium content was 12 wt.%, the hardness of alloy reached the highest value of 61.1 HRC, and the wear resistance of alloy was the best. The results of worn surface analysis showed that the wear failure of as-cast Fe-Cr-B alloy was mainly caused by multiple plastic deformation and micro-cutting. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the effect of titanium modification on microstructures and properties of carbidic austempered ductile iron (CADI) containing 3.72 wt.% C, 2.77 wt.% Si, and 0.51 wt.% Mn. The results showed that with the addition of 0.1 wt.% Ti, TiC particles were formed, and distributed in carbides and matrix. Microstructural observation indicated that the maximum diameter of graphite nodules decreased from 58 to 40 μm, and the shape of carbides transformed from network to fragmentation, which was related to the nucleation of the eutectic structure (γ + (Fe, Cr)3C) where TiC particles act as the nucleus. After isothermal quenching at 300 °C, the hardness of Ti-bearing CADI was 3.5 HRC higher than ordinary CADI, and the impact toughness was increased by 14.3%. Additionally, due to the decrease in exfoliation, the wear loss of Ti-bearing CADI was 14.8% lower than ordinary CADI during the block-on-ring wear test at the surface load of 300 N. [ABSTRACT FROM AUTHOR]

The microstructure and oxidation kinetics of Fe-B-based alloys at 927 K in air with different boron concentrations of 0.95, 1.45, 2.10, and 3.08 wt% were studied. The alloy microstructures were interpreted to consist of α-Fe, FeB, and pearlite. After 100-h oxidation, the oxides comprised FeO at the surfaces and a mixed BO-SiO layer at matrix/oxide interface. The formation of mixed oxides layer was affected by boron content in the alloy and had obvious influence on the oxide morphology. The isothermal oxidation kinetics at 973 K exhibited initial rapid mass loss followed by slow mass loss, and the oxidation rate constants of the two oxidation stages demonstrated completely opposite tendencies with the increase of boron. The Fe-B 3.08 wt% alloy exhibited the best oxidation resistance after 100 h of cyclic oxidation due to the formation of a well-distributed and continuous BO-SiO mixed oxide layer. [ABSTRACT FROM AUTHOR]

The effects of titanium and nitrogen elements on the microstructure and impact toughness of the Fe-B alloy have been studied. The results show that the borides are refined after the additions of titanium and nitrogen elements. With the additions of titanium and nitrogen, titanium nitrides are formed in the Fe-B alloy. Titanium nitride can act as effective heterogeneous nuclei of primary austenite, and promote the refinement of austenite and boride. After heat treatment, the impact toughness of Fe-B alloys modified by titanium and nitrogen elements is higher than that of ordinary alloy. [ABSTRACT FROM AUTHOR]

The microstructures of Fe-B alloys containing different carbon and boron concentrations have been investigated. The solidification microstructures of Fe-B alloy consist of the eutectic boride, pearlite, and ferrite. Borides precipitate along the grain boundary during the formation of eutectic. After heat treatment, the phases in Fe-B alloy are composed of the boride and martensite. With increase of carbon and boron concentrations, the Rockwell hardness of Fe-B alloy becomes larger. Meanwhile, by using a pin-on-disk abrasion tester, the effects of carbon and boron concentrations on the wear behaviors including ploughing depth, roughness, and wear weight loss under different loads have been studied. The results show that the wear resistance of Fe-B alloy with higher carbon and boron concentrations is comparable with the high chromium white cast iron. [ABSTRACT FROM AUTHOR]